The invention relates to assays for detecting cross-linked telopeptide analytes indicative of type II collagen (cartilage) resorption in vivo, and in particular provides immunoassays for measuring and distinguishing between resorption of non-mineralized cartilage and mineralized cartilage, and for measuring total cartilage resorption in vivo.
BACKGROUND OF THE INVENTION
Reference is made to the applicant""s prior U.S. Pat. Nos. 4,973,666, 5,140,103, 5,300,434, 5,320,970, 5,817,755, and 5,702,909, which are incorporated by reference herein.
Immunoassays are known for detecting telopeptide analytes indicative of collagen resorption in vivo. Examples of such type I collagen assays for measuring bone resorption include: WO 89/04491 (Eyre); WO 89/12824 (Robins); WO 91/08478 (Eyre); EP 0505210 A2 (Risteli and Risteli); WO 92/21698 (Eyre); WO 94/03813 (Naser et al.); WO 94/14844 (Baylink); WO 95/04282 (Naser et al.); WO 95/08115 (Qvist and Bonde); WO 96/12193 (Bonde and Qvist); EP 0718309 A1 (Naser et al.); and WO 96/36645 (Eyre et al.).
Examples of type II collagen telopeptide assays for measuring cartilage resorption include WO 91/08478 (Eyre); WO 95/08115 (Qvist and Bonde); and WO 96/12193 (Bonde and Qvist).
Examples of type III collagen telopeptide assays include WO 88/08980 (Risteli and Risteli) and WO 91/08478 (Eyre).
The following patent disclosures are also of interest: U.S. Pat. No. 4,628,027 (Gay) discloses in vitro diagnostic methods using monoclonal antibodies against connective tissue proteins. U.S. Pat. No. 5,316,914 (Oshima et al.) discloses an enzyme sandwich immunoassay of human type III, IV, and VI collagens applicable to diagnosis of hepatic diseases. WO 94/14070 (Poole and Hollander) discloses an immunoassay for the measurement of collagen cleavage in cartilage. WO 94/18563 (Barrach et al.) discloses sandwich immunoassay methods for detecting type II collagen derived peptides associated with arthritis.
Of particular interest is the applicant""s prior international publication, WO 91/0478, which discloses the following urinary resorption products of type II collagen 
wherein the parentheses indicate optional amino acid residues, and the cross-linking residue depicted as Hyl-Hyl-Hyl is hydroxylysyl pyridinoline (HP), a natural 3-hydroxypyridinium residue present in mature collagen fibrils of various tissues. These analytes derive from the C-terminal cross-linked telopeptide domain of type II collagen and so are collectively referred to herein as xe2x80x9ccol2CTxxe2x80x9d.
The present disclosure also adopts the one-letter symbol form of amino acid shorthand; thus, the Glu-Hyl-Gly-Pro-Asp-(Pro)-(Leu) telopeptide components of the analytes shown above are referred to hereinafter as EKGPD (SEQ ID NO:1), EKGPDP (SEQ ID NO:2), and EKGPDPL (SEQ ID NO:3). Furthermore, as used herein the symbol xe2x80x9cKxe2x80x9d represents either lysine, in the case of linear peptides, or a cross-linking 3-hydroxypyridinium residue selected from among hydroxylysyl pyridinoline (HP) and lysyl pyridinoline (LP).
The applicant and colleagues have also described col2CTx in recent abstracts:
Eyre et al., Bone Miner. Res. 11(S1): S413, 1996, describes cross-linked telopeptides from collagen types I, II, and III in human urine.
Atley et al., Arth. Rheum. 40(9S):584, 1997, reports that RS-130830, a selective inhibitor of collagenase-3, blocks the release of hydroxyproline and a metalloproteinase (MMP) specific neoepitope, col2CTx, from bovine cartilage exposed to IL- 1xcex1.
Atley et al., Trans. Orthop. Res. Soc., New Orleans, 1998, reports matrix metalloproteinase-mediated release of immunoreactive telopeptides from cartilage type II collagen. The aim of this study was to evaluate whether an immunoassay based on a monoclonal antibody (mAb) 2B4, which recognizes a domain of the xcex11(II) C-telopeptide EKGPDP, measures MMP cleavage products in cartilage. The mAb 2B4 recognizes the in vitro product of matrilysin digestion AFAGLGPREKGPDP (SEQ ID NO:4) of synthetic peptide AFAGLGPREKGPDPLQYMRA (SEQ ID NO:5), but not AFAGLGPREKGPDPLQ (SEQ ID NO:6), AFAGLGPREKGPDPLQY (SEQ ID NO:7), LQYMRA (SEQ ID NO:8), or YMRA (SEQ ID NO:9). The authors also noted detection of mAb 2B4 immunoreactivity in synovial fluid, serum, and urine. They concluded that this 2B4 epitope has the potential to be a useful marker of type II collagen resorption in vivo.
Moskowitz et al., Amer. Coll. Rheum., San Diego, Calif. Nov. 8-12, 1998, reports that the type II collagen C-telopeptide 2B4 epitope is a marker for cartilage resorption in familial osteoarthrosis.
Eyre et al., Combined Orthopaedic Research Societies Meeting, Vittel, France, Sept. 28-30, 1998, discusses biochemical markers of bone and collagen degradation, including a cross-linked telopeptide product of type II collagen degradation in urine (col2CTx).
Atley et al., Combined Orthopaedic Research Societies Meeting, Hamamatsu, Japan, 1998, discusses collagen type II cross-linked telopeptides, a promising marker for cartilage degradation in arthritis.
In addition, monoclonal antibodies to the C-telopeptide of type II collagen as diagnostic markers for rheumatoid arthritis are reportedly under development at Osteometer Biotech A/S. BioWorld International, page 3, Dec. 3, 1997.
The entire disclosures of the prior scientific and patent publications cited in this patent application are incorporated by reference herein.
The invention provides improved assays for measuring type II collagen (cartilage) resorption in vivo. The subject immunoassays are useful for distinguishing between resorption of non-mineralized cartilage and mineralized cartilage, and for measuring total cartilage resorption in vivo. The disclosed immunoassays employ either one or a combination of two antibodies. A first antibody binds to DEKAGGA (SEQ ID NO:21) but not to GGFDEKAGGAQLG (SEQ ID NO:27), where the K symbols refer to lysine residues and/or preferably to cross-linking 3-hydroxypyridinium residues. Measurement of analyte binding to the first antibody in serum provides an indication of non-mineralized cartilage resorption in vivo.
A second antibody binds to GGFDEKAGGAQLG but not to DEKAGGA, where the K symbols also preferably refer to cross-linking 3-hydroxypyridinium residues. Measurement of analyte binding to the second antibody in serum provides an indication of mineralized cartilage resorption in vivo.
An indication of total (non-mineralized and mineralized) cartilage resorption in vivo is provided by either measurement of analyte binding to the first antibody in urine, or by measurement of the total analyte binding to the first and second antibodies in serum.
The subject cartilage markers are preferably measured in conjunction with bone collagen resorption markers selected from among amino-terminal telopeptides of type I collagen, carboxy-terminal telopeptides of type I collagen, and free lysyl pyridinoline (deoxypyridinoline) cross-links.